Machine Components of Speed Frame

Machine Components of Speed Frame

The important parts of speed frame are given as follows:

❶ Bottom rollers

❷ Rubber-covered top rollers

❸ Top arm

❹ Aprons (top and bottom)

❺ Spacer

❻ Condenser (inlet and floating)

❼ Top arm

❽ Flyer

❾ Spindle

❿ Pressure arm

 Top Rollers

 Top rollers are held strictly parallel to and in perfect alignment with bottom rollers.

 Top rollers covered with rubber cots play a significant role in the control of drafting irregularities.

 The hardness of top rollers is between 80° and 85° Shore, but the rollers over which the apron runs often have a hardness only slightly above 60° Shore. This permits better enclosure and guidance of the fiber strand during drafting.

 The top rollers must be pressed with relatively high force against the lower rollers to ensure guidance of the fibers. 100- 300 N per roller is normally applied depending on raw material and volume of fibers.

 The fiber or dust accumulation in the top roller neck should be cleaned frequently using picker gun.

 Bottom Rollers

 Bottom rollers are made of steel

 The bottom rollers of speed frame exercise immense influence on the quality of roving.

 Precise concentricity of a bottom roller is a function of improved roving quality (evenness and strength).

 Bottom rollers having narrow tolerances of dimensions B, p, and T (Figure) produce fault-free roving.

 Eccentric or damaged bottom rollers, especially front bottom rollers, are the most common cause of unnecessary roving faults and excessive roller laps.

 Top Arm

Spring loaded top arms are normally adopted in speed frame to get optimum pressure on top rollers to achieve required quality and performance. The top arm pressure and roller setting influence the roving quality and subsequently yarn quality.

 Aprons

 Aprons are one of the most effective means to support the floating fibers and drastically reduce the drafting wave.  Apron wear is accelerated by high drafts and sliver linear density.

 It is essential that the aprons should extend as closely as possible to the nip line of the front rollers.

The top apron is short and made of synthetic rubber that has a thickness of about 1 mm. Bottom apron is larger and made of the same material as the upper one.
 Basically, synthetic aprons are made in an endless tubular form whereas leather aprons are made in open strips that are subsequently glued together to form an apron.

 The advantage of tubular construction is seamless and uniform along its circumference.

 The length of the aprons also called as the cradle length is kept approximately equal to the staple length of the fibers. The cradles for different staple length are shown in Figure.

 Cradle lengths according to the fiber length

                       

 Spacer

The distance between top and bottom aprons is maintained by a small component called “cradle spacer” or “spacer,” which is inserted between the nose bar of the bottom apron and the cradle edge of top apron. The selection of spacer for a process depends on the hank of the sliver, break draft, and roving hank.

Spacer size of different roving hanks                                

Advantages and disadvantages of reducing the spacer size

 Condenser

 Condensers placed in the drafting zone help to prevent the fiber strand from spreading apart during drafting.

 Condensers can be classified as feed (or inlet) condenser, middle condenser, and delivery (or floating)  condenser (Figure).

 Feed condenser is used just before the back pair of drafting rollers. The middle condenser is used near the nip of the middle pair of rollers and the third one is used just before the front pair of rollers.

 The main function of the feed condenser is to lead the sliver properly into the drafting arrangement.

 The main function of the last two guides is to bring back the fiber mass into a strand that tends to tear apart because of the drafting action.

 The size of condensers should be selected according to the volume of the fiber sliver (Table).

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